namespace AllowPrivate
{
    class Program
    {
        static void Main(string[] args)
        {
            MyTest t = new MyTest();
            t.SetId(Guid.NewGuid());

            var output = JsonSerializer.ToJsonString(t, StandardResolver.AllowPrivateExcludeNull);
            var input = JsonSerializer.Deserialize<MyTest>(output, StandardResolver.AllowPrivateExcludeNull);
            Debug.Assert(t.Id == input.Id);
        }
    }

    public abstract class TestBase
    {
        public Guid Id { get; protected set; }
    }

    public class MyTest : TestBase
    {
        public void SetId(Guid id)
        {
            Id = id;
        }
    }
}